A most important characteristic of an intelligent network, which is a kind of architecture applied for producing and providing services, is that various special value-added services can be provided rapidly, conveniently, flexibly and economically. Moreover, service control and charging are performed separately by an Online Charging System (OCS) which is locally or globally used by more and more operators currently.
A Pre-Paid Service (PPS) is regarded as a fundamental and the most important service content provided by each operator and the quality of a voice service directly influence profits and benefits of the operator. For a mobile network, a Customized Applications for Mobile Network Enhanced Logic (camel) protocol has been supported in most countries. However, due to different economic conditions, the phases of camel are different, some are in the camelphase1 (camel1 for short), some are in the camelphase2 (camel2 for short) and the others are in the camelphase3 (camel3 for short). Aiming at these three different network types, the voice call service should be developed using a corresponding network protocol signalling to adapt to the network types. For those operators using earlier camel phases, the network in an earlier camel phase is updated to a network in a later camel phase, according to a traditional service development process, the voice call service should also be updated and rebuilt so that the corresponding camel protocol is used thus inevitably increasing the development and maintenance costs and lowering the operation efficiency.
In addition, for some operators which determine to use higher camel types, there are also problems existing in their call services, e.g. if an operator adopts the camel3 network type and all the voice call services within the network coverage of the operator adopt signalling corresponding to camel3, however, when the voice call services roam to other countries or environments the network type of which are a camel1/camel2, the signalling required to be processed will turn into a signalling of camel1/camel2, so a roamed call cannot be processed or supported in the voice call services.